21356439 has 8 divisors (see below), whose sum is σ = 30665712. Its totient is φ = 13142400.

The previous prime is 21356431. The next prime is 21356453. The reversal of 21356439 is 93465312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21356439 - 2³ = 21356431 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21356431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 273762 + ... + 273839.

It is an arithmetic number, because the mean of its divisors is an integer number (3833214).

Almost surely, 2^21356439 is an apocalyptic number.

21356439 is a deficient number, since it is larger than the sum of its proper divisors (9309273).

21356439 is a wasteful number, since it uses less digits than its factorization.

21356439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 547617.

The product of its digits is 19440, while the sum is 33.

The square root of 21356439 is about 4621.3027384061. The cubic root of 21356439 is about 277.4446022035. Note that the first 3 decimals are identical.

It can be divided in two parts, 213564 and 39, that multiplied together give a square (8328996 = 2886²).

The spelling of 21356439 in words is "twenty-one million, three hundred fifty-six thousand, four hundred thirty-nine".